An XFP optical transceiver as shown in PATENT LITERATURE 1, for example, has been in practical use as an optical module in an optical communication network. The XFP optical transceiver is provided with an optical connector receptacle, and a circuit board to which a transmission module and a reception module are attached in a housing.
Moreover, as shown in PATENT LITERATURE 2, on demands for a lower profile of an optical module and for high-density packaging in the optical module, there has also been proposed an optical module which comprises: a first board provided with an optical semiconductor element; a second board provided with a semiconductor element for driving the optical semiconductor element and amplifying signals, and an electrical connector for input and output of electrical signals to outside; and a bendable flexible cable configured to electrically connect an end portion of the first board and an end portion of the second board. In addition, an MT connector having an MT ferrule serving as an optical connector as shown in PATENT LITERATURE 2, for example, has been in practical use. In the MT connector, because optical coupling between an optical semiconductor element and an optical fiber is dependent on positional accuracy of attaching guide pins as suggested in PATENT LITERATURE 2, the guide pins need to be mounted on a board with high accuracy. Accordingly, the board needs to have prescribed hardness.